Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
  • G03B21/14—Details
  • G03B21/20—Lamp housings
  • G03B21/2053—Intensity control of illuminating light
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
  • G03B21/14—Details
  • G03B21/20—Lamp housings
  • G03B21/2006—Lamp housings characterised by the light source
  • G03B21/2033—LED or laser light sources
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
  • G03B21/14—Details
  • G03B21/20—Lamp housings
  • G03B21/2086—Security or safety means in lamp houses
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N9/00—Details of colour television systems
  • H04N9/12—Picture reproducers
  • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
  • H04N9/3141—Constructional details thereof
  • H04N9/315—Modulator illumination systems
  • H04N9/3161—Modulator illumination systems using laser light sources
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N9/00—Details of colour television systems
  • H04N9/12—Picture reproducers
  • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
  • H04N9/3191—Testing thereof
  • H04N9/3194—Testing thereof including sensor feedback
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B17/00—Details of cameras or camera bodies; Accessories therefor
  • G03B17/48—Details of cameras or camera bodies; Accessories therefor adapted for combination with other photographic or optical apparatus
  • G03B17/54—Details of cameras or camera bodies; Accessories therefor adapted for combination with other photographic or optical apparatus with projector
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
  • G03B21/14—Details

Definitions

• the invention relates to the field of devices for projecting images on a projection screen providing eye-protection features. It is particularly adapted to laser- based image projection subsystems.
• Projectors are devices adapted for projecting image information from different sources on a surface.
• the image information can be still images (photographies, slides, computer displays, etc.) or moving (videos, animations, etc.) and can be provided by different sources like, for instances, a computer connected to the projection device, multimedia player (DVD, Blueray players), TV tuner, etc.
• multimedia player DVD, Blueray players
• TV tuner etc.
• the projector subsystem can also be embedded inside a communication terminal like a smartphone, a tablet, a laptop computer, etc. and then be able to use the content of the communication system as sources and project any files stored inside the communication system.
• This type of projector is usually referred to as "pico- projector", and is constrained in size and power consumption so as to be embedded in a more complex system, often a handheld device.
• Projectors including pico-projectors, are often based on laser technology for projecting images. Usually, one laser per color component (red, green, blue) is used.
• lasers (as well as light beams above a certain power) may be armful or dangerous when directed towards the eyes.
• the patent application US2010/0177929 proposes a solution where the projector device also comprises a camera to capture the projected image. The device then analyses the image and uses face-recognition algorithms to determine if a human face (or other body features) is present and in this case switch off the projection beam.
• a major drawback of this solution is the confusion that can be made between a real human face and a projected human face.
• the camera is unable to make this distinction and this mechanism detects the presence of a human in front of the projector each time the projected image contains a human face (or any other human body feature used to detect a human presence).
• An object of embodiments of the present invention is to alleviate at least partly the above mentioned drawbacks. More particularly, embodiments of the invention aim at improving the situation by enabling to robustly and safely projecting an image from a projection subsystem without increasing dramatically its manufacturing cost.
• a first object of the invention is a method for safely projecting an image comprising steps of:
• the depth view can be computed from a pair of images provided by a pair of stereoscopic cameras.
• the step of determining if a human is in front of the projector may comprise sub-steps of:
• Delimiting areas within the depth view may consist in determining a base depth within this depth view corresponding to the projection surface and groups of points within the depth view, having a depth substantially different the previously determined base depth.
• Tuning said projector accordingly may consist in switching it off, if a human is detected as being in front of said projector.
• the body feature may be a human face and, in this case, detecting that a human is in front of said projector can consist in detecting that this human is facing the projector.
• Another object of the invention is a projection subsystem comprising a projector for projecting an image on a projection surface and a safety feature for tuning the projector when a human is detected in front of it.
• the safety feature comprises:
• the apparatus may comprise a pair of stereoscopic cameras providing a pair of stereoscopic images from which the depth view is computed.
• the computing circuits may comprise means for:
• These means may be adapted to delimit areas within said depth view by determining a base depth corresponding to the projection surface and grouping points within this depth view, having a depth substantially different from the previously determined base depth.
• the safety feature can adapted to switch the projector off when a human is detected as being in front of the projector.
• the camera (used for acquiring the captured image) may be one among the pair of stereoscopic cameras.
• the body feature may be a human face and detecting that a human is in front of said projector may consist in detecting that the human is facing the projector.
• Another object of the invention is a communication terminal comprising a projection subsystem as previously defined, potentially with any of its possible embodiments.
• Another object of the invention is a computer program product comprising a computer readable medium, having thereon a computer program comprising program instructions, the computer program being loadable into a data-processing unit and adapted to cause execution of the method previously described with some variants, when the computer program is run by the data-processing unit.
• Fig. 1 shows a projection subsystem adapted to implement embodiments of the invention.
• Fig. 2 shows a communication terminal adapted to implement embodiments of the invention.
• Fig. 3 represents a block diagram illustrating an exemplary configuration of a projection subsystem according to embodiments of the invention.
• Fig. 4 shows a schematic example of a depth view, in accordance with an embodiment of the invention.
• Fig. 5 illustrates the context in which a projection subsystem according to embodiments of the invention can be deployed.
• Fig. 6 represents a flow chart of a method for safely projecting an image in accordance to an embodiment of the invention.
• FIG. 1 On the figure 1 is depicted a projection subsystem PSS adapted for projecting multimedia content (photos, videos, graphics%) or textual content (texts, figure sheets%) in different contexts (home entertainment, business, etc.) as still or moving images.
• PSS projection subsystem
• the images are actually projected by a projector.
• the projector P is an optical device which generally makes use of laser technologies. Some may uses other technologies, like LED, but they have been widely criticized for having insufficient brightness for everyday use in a normally lit room.
• a laser-based projector uses three laser beams, one per color components (red, green, blue).
• the projection subsystem PSS can comprises other circuitries like Codecs, memory (for storing multimedia contents, for instance), and memory and processing means to implement various features.
• the projection subsystem PSS can comprise a safety feature that will be described later.
• This projection subsystem PSS can be a stand-alone device product, aiming at being put on a table, like depicted in the figure 1.
• the communication terminal may be a tablet, a smartphone, a mobile phone, etc. It comprises a man-machine interface which may comprise a screen S (which is typically a touchscreen) and buttons B.
• the projection subsystems PSS also comprises a pair of stereoscopic cameras CI, C2. These two cameras are adapted to provide the projection subsystems PSS with a pair of stereoscopic images of a same captured view.
• the cameras CI, C2 and the projector P should ideally be aligned. In case of bad alignment (or other position), an extra processing is needed to compensate it.
• the projection subsystem PSS can comprise other sensors instead of or in addition to these stereoscopic cameras.
• the sensors should be adapted to provide data enabling the computing of a depth view of the projection surface.
• these sensors can be a camera associated with a structured-light emitter.
• the structured light may be in the infrared domain like with the product "Kinect”TM of the company Microsoft.
• this embodiment provides the further advantage of enabling the verification by a third camera's image the depth view information deduced from a pair.
• the figure 3 represents a possible high-level architecture of a projection subsystem PSS (being a stand-alone one, or embedded inside a communication terminal).
• the projector P embedded within the projection subsystem PSS is adapted to obtain an image to project IMG at step S 1.
• the source of this image can be internal to the projection subsystem PSS which can comprise a internal memory (flash RAM, hard disk%) to store some contents, or a removable memory (cards, USB key, etc.).
• a internal memory flash RAM, hard disk
• a removable memory cards, USB key, etc.
• the projector P is actuated to project this image on a projection surface, in a step S2.
• the way the projector is actuated depends on the technology and on the model of the projector itself and is out of the scope of the present invention.
• the projector surface can be any surface available to the user of the projection subsystem PSS. In the ideal case, it is a plan surface with an uniform clear color (white, preferably) and a smooth texture. However, in the situation where the projection system is a handheld device (including a communication terminal), the user may face different situations where he cannot find an ideal projection surface and where he should project the image on rough-texture walls, grey-colored surfaces or even non-planar surfaces.
• FIG. 5 On figure 5 is depicted a projection surface PS on which a projection subsystem PSS projects an image PI.
• the projection subsystem PSS also comprise a safety feature FS for tuning the projector when a human is detected in front of the projector P.
• This safety feature comprises itself some apparatuses for computing, in a step S3, a depth view DV corresponding to at least a portion of the projection surface PS.
• This portion corresponds to a zone of danger, i.e. the zone where it is desirable to avoid projecting the image by actuating the laser beams in case a human is present.
• the size of this portion may correspond to the projected image PI surrounded by a security zone.
• This security zone can be a built-in parameter or tunable through a man-machine interface of the projection subsystem. It can be a percentage of the projected image and its value may depend on the actual technology of the projector P.
• the portion may include an even larger zone, to strengthen the safety of the system.
• a larger portion may provide the further advantage to anticipate the behavior of humans who are outside a zone of danger at one moment but may enter it the second after. By taken into account humans outside the zone of actual danger, the safety feature may tune down the projector before they enter.
• the depth view DV may be computed from a pair of images provided by stereoscopic cameras CI, C2 by a stereoscopic processing unit SPU within the safety function SF.
• This stereoscopic processing unit SPU can implement known technologies of stereopsis or computer stereo vision. Basically, it may implement a 2-step algorithm consisting in:
• the first step can be done for instance by using known pattern-matching algorithms.
• the second step can be better understood by the figure 7.
• Two stereoscopic cameras CI, C2 takes two images of the same scene and, in particular, of a point P of the projection surface PS. As these cameras have different location, they view the point P with different angles. More concretely, the image acquired from the camera CI shows the point P as projected along the projection line pi onto a virtual plan VP, whereas the image acquired from the camera CI shows this same point P as projected along the projection line p2 onto this virtual plan VP.
• the distance d between the two projections on the virtual plan VP is directly representative of the depth h.
• This depth h represents the distance of this point P to this virtual plan VP.
• this virtual plan is a parameter which can be arbitrary set, the depth h has only a relative meaning. This relative meaning is however sufficient to estimate the shape of the projection surface PS, but iterating this process on a sufficient sample of points P. The result of these iterations provides the depth view information DV.
• the depth view is transmitted to computing circuits CC.
• the computing circuits CC perform a step S5 of delimiting areas within said depth view. These areas corresponds to entities different from the projection surface PS but present in front of the projector P. They thus represent situations of risks.
• the figure 4 schematically represents a depth view DV corresponding to the line segment AX of the figure 5. According to usual convention, the lowest values correspond to the most distant points, while higher values correspond to closer points.
• the depth view In real situations where the depth view is computed for a 2D projection surface (or portions of it), the depth view forms a 3D data structure.
• the depth view is a 2D data structure since based on a line segment: the "real" depth view can be reconstructed by joining all horizontal line segments of the projection surface PS so as to finally get the 3D data structure.
• the axis x represents the position along the line segment AX and the axis DV represents the value of the depth view for a given position.
• the base depth can be determined in various ways.
• the user can put a special marker on the projection surface to calibrate the depth view and set the base depth.
• the user can enter the value of an (estimated) base depth, settable through the man-machine interface associated with the projection subsystem.
• Still another solution the user can be asked to capture a reference depth view when nothing else than the data projected is in the laser area risk. In this case, this is up to the end user to guarantee this capture and to enable the security system through a Man-machine interface.
• an image processing algorithm can be deployed in order to detect geometrical features within the depth view information which may correspond to an eligible projection surface.
• the computing circuits CC can delimit areas within the depth view DV which can be defined by groups of points having a depth substantially different from the base depth.
• an area can be determined as corresponding to the object F2.
• the value associated to the term “substantially” is a threshold value depending on the precision of the computed depth view (and also on the measurements made by the cameras CI, C2) and also set so as to avoid taking into account riddles of the projection surface PS.
• Another threshold can also be considered to filter out areas of an insufficient size: a detected object only a few centimeters wide cannot be considered as being a human being and should not be considered as a potential risk.
• a new step S3 of computing the depth view can be triggered.
• This enables continuously monitoring the space in front of the projector P.
• the start of a new step S3 can follow immediately the end of the steps S3 or S7, or, be triggered by a timer so as to have a new scan (i.e. computing of the depth view) according to a preset periodicity. If at least one area can be delimited, it means that an object is present in front of the projector P and that there is a potential risk.
• this step S5 does not distinguish between humans and objects. For instance, a chair put in front of the projector P will be detected by this step based on the depth view. In order to provide more robustness and avoid undesirable false alarms, further steps are provided by embodiments of the invention.
• the computing circuits CC can apply a body feature recognition algorithm on these areas in a step S6.
• the body feature is a human face, so as to detect that a human is facing the projector P. This is particularly useful since the main danger is to avoid the laser beams to enter the eyes of the user.
• the face recognition algorithms that can be used may be algorithms of the state of the art. Many such algorithms have been proposed so far, for example in the technical domain of the photography where one wishes the camera to automatically focus on the faces present in front of the camera.
• the body recognition algorithm may take as input not only the areas previously delimited by also a captured image.
• This captured image CI can be acquired by a camera (at step S4).
• This camera can be one among the pair of stereoscopic camera CI, C2.
• the image captured by the camera CI is used as input to the computing circuits CC.
• the computing circuits CC can then delimit the corresponding areas within the captured image, and run the body recognition algorithm on them.
• the captured image CI can represent the same portion of space than the one captured for computing the depth view. The smaller of both will form the considered space within which risk can be detected.
• the step S7 consists then in detecting that a human is present in front of the camera. If no, the process can loop back to the step S3.
• step S8 consists in having the computing circuits CC sending the appropriate commands to the projector P to tune it accordingly.
• Tuning may mean to dramatically reduce the intensity of the laser beams down to a safe level. It may also mean to shut it down completely.
• Other embodiments include a partial switch-off or "blanking" of the concerned part of the projected image PI which comprises the detected human (e.g. body features), like for instance described in the patent application US 2010/0177929.
• the projector can make use of different technologies, it may also mean that the projector P switch from the laser technology to LED technology for instance.
• the process can then be back to the step S3 in order to go on scanning the risky space.
• step S8 may consist in turning back the projector on, or to tune it to the normal intensity.
• a second face Fl has been depicted.
• This face is a graphic element part of the projected image PI (which can be a photograph or a video). Thanks to the invention based on a computation of a depth view, this face Fl does not generate any false alarm, since the depth view DV is not impacted by any picture information of the projected image PI and since the body feature recognition algorithm is applied only on the areas firstly delimited on the basis of the depth view DV.
• the invention has been described with reference to preferred embodiments.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Computer Security & Cryptography (AREA)
• Controls And Circuits For Display Device (AREA)
• Testing, Inspecting, Measuring Of Stereoscopic Televisions And Televisions (AREA)
• Projection Apparatus (AREA)

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• 2013
  • 2013-01-24 EP EP13305081.5A patent/EP2696586A1/de not_active Withdrawn
  • 2013-07-17 US US14/413,548 patent/US9500939B2/en active Active
  • 2013-07-17 WO PCT/EP2013/065059 patent/WO2014023538A1/en active Application Filing

Patent Citations (4)

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